N-thioacyl homoserine lactone compound and preparation method thereof

Abstract

The invention belongs to the technical field of medicinal chemistry, and particularly relates to an N-thioacyl homoserine lactone compound and a preparation method thereof, the compound is an analogue of a natural self-inducer N-acyl homoserine lactone AHLs, and thioamide is used as a biological isostere of amide to replace an amide group in the natural self-inducer. The compound has an obvious inhibition effect on a Vibrio fischeri Lux system and related toxic gene phenotypes regulated by the Vibrio fischeri Lux system and can be used as a Vibrio fischeri quorum sensing activity inhibitor, and thioamide is more stable in chemical structure than dithiocarbamate and has better enzyme hydrolysis stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of medicinal chemistry, and particularly relates to an N-thioacyl homoserine lactone compound and a preparation method thereof. Background Art

[0002] Bacterial quorum sensing, also known as cell density-dependent gene expression, is a crucial mechanism by which bacteria, acting as a group, coordinate their responses to the external environment or host, enabling intercellular communication. This mechanism provides a novel approach to understanding the mechanisms regulating pathogenicity and developing new antimicrobial agents. This intercellular communication is mediated by chemical signaling molecules, of which N-acyl homoserine lactones (AHLs) are a class of chemical signaling molecules unique to Gram-negative bacteria. These water-soluble, membrane-permeable molecules are produced by bacteria. When a critical concentration of these signaling molecules reaches the environment, they bind to receptor proteins to form ligand complexes, acting as transcriptional activators that regulate gene expression, including virulence factors. With the increasing prevalence of bacterial drug resistance, the search for new antimicrobial agents has become a pressing scientific challenge in medicinal chemistry, with practical implications for addressing the growing problem of pathogen resistance. By inhibiting quorum sensing in pathogens and reducing their toxicity, the host's immune system can clear the infection or use a reduced dose of antimicrobial agents to combat the infection, mitigating the development of bacterial resistance. Compared with traditional fungicides, bacterial quorum sensing inhibitors are thought to have fewer side effects on non-target organisms.

[0003] Patent application number 201710475934.4 discloses phenylurea-substituted N-thioacylhomoserine lactone compounds, their preparation methods, and applications. These compounds, which are dithiocarbamates, exhibit significant inhibitory effects on the LAS and PQS systems of Pseudomonas aeruginosa. Using bioisostere theory, these AHL analogs were synthesized, targeting the LuxR system of Vibrio fischeri and inhibiting its quorum sensing activity, specifically its bioluminescent gene phenotype. This research has not been reported in the literature. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to provide an N-thioacyl homoserine lactone compound with antibacterial quorum sensing activity and a preparation method thereof.

[0005] To achieve the above objectives, the technical solutions of the present invention are as follows:

[0006] In a first aspect, the present invention provides an N-thioacyl homoserine lactone compound, which is used to inhibit bacterial quorum sensing activity, and has the general chemical formula:

[0007]

[0008] In the above formula, Ar is an aromatic group; Alkyl is an alkyl group.

[0009] The N-thioacyl homoserine lactone compound is selected from any one of the following:

[0010] Compound a:

[0011]

[0012] Compound b:

[0013]

[0014] Compound c:

[0015]

[0016] Compound d:

[0017]

[0018] Compound e:

[0019]

[0020] Compound f:

[0021]

[0022] Compound g:

[0023]

[0024] The N-thioacyl homoserine lactone compound is used for inhibiting the quorum sensing activity of Vibrio fischeri.

[0025] In a second aspect, the present invention provides a method for preparing an N-thioacyl homoserine lactone compound, the preparation method comprising:

[0026] Step 1: dissolving L-homoserine lactone salt and carboxylic acid in a container, adding triethylamine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1-hydroxybenzotriazole monohydrate to the container to react to obtain an intermediate product;

[0027] Step 2: reacting the intermediate product with Lawesson's reagent to obtain the target product, namely, N-thioacyl homoserine lactone compound.

[0028] The carboxylic acid is selected from any one of the following: p-bromophenylacetic acid, p-bromobenzoic acid, hexanoic acid, p-nitrophenylpropionic acid, p-bromophenoxyacetic acid, p-methylbenzoic acid, cinnamic acid, and p-nitrophenylpropionic acid.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The N-thioacylhomoserine lactone compounds described in the present invention are analogues of the natural autoinducer N-acylhomoserine lactone AHLs. They use thioamide as the bioisostere of amide to replace the amide group in the natural autoinducer, target the LuxR system of Vibrio fischeri, and have a significant inhibitory effect on the quorum sensing activity of Vibrio fischeri. They have high biological activity, and thioamide is more stable in chemical structure than dithiocarbamate and has better enzymatic hydrolysis stability. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to specific embodiments.

[0032] The present invention first uses L-homoserine lactone salts and different carboxylic acids to prepare a series of intermediate acyl homoserine lactones. The amide groups on the acyl homoserine lactones are then sulfamidated using Lawesson's reagent, resulting in the synthesis of thioacyl homoserine lactones in a single step. The overall synthesis method is simple, has mild reaction conditions, is easy to operate, and is suitable for large-scale production. The synthesis steps are as follows:

[0033]

[0034] Example 1:

[0035] Step 1: In a round-bottom flask, 2.0 mmol of p-bromophenylacetic acid and 2.4 mmol of L-homoserine lactone salt were dissolved in 9 mL of dichloromethane solvent. 4.4 mmol of triethylamine, 2.2 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), and 2.0 mmol of 1-hydroxybenzotriazole monohydrate (HOBt) were added sequentially at 0°C. The reaction system was stirred at room temperature for 16 hours. After the reaction, the dichloromethane solvent was removed and 20 mL of ethyl acetate was added. The mixture was washed sequentially with 1% HCl, 5% NaHCO3, and saturated brine, dried over anhydrous sodium sulfate, and distilled under reduced pressure to obtain a white solid with a yield of 93%.

[0036] Step 2: The white solid obtained in step 1 and Lawesson's reagent were dissolved in 7 mL of dry toluene at a molar ratio of 1:0.6. The mixture was heated in an oil bath at 70°C for 5-6 h, and water was added to terminate the reaction. After removing the solvent, 10 mL of ethyl acetate and 10 mL of saturated NaHCO3 were added and stirred for 10 min. After separation and extraction, the mixture was evaporated under reduced pressure and separated by column chromatography (ethyl acetate: petroleum ether = 2:1) to obtain the target product, i.e., compound a, with a yield of 80%.

[0037] Example 2:

[0038] By replacing p-bromophenylacetic acid with hexanoic acid, the target product is finally obtained as compound b.

[0039] Example 3:

[0040] By replacing p-bromophenylacetic acid with p-bromophenylacetic acid, the target product is finally obtained as compound c.

[0041] Example 4:

[0042] By replacing p-bromophenylacetic acid with p-bromophenoxyacetic acid, the target product, compound d, was finally obtained.

[0043] Example 5:

[0044] By replacing p-bromophenylacetic acid with p-toluic acid, the target product is finally obtained as compound e.

[0045] Example 6:

[0046] By replacing p-bromophenylacetic acid with cinnamic acid, the target product, compound f, was finally obtained.

[0047] Example 7:

[0048] By replacing p-bromophenylacetic acid with p-nitrophenylpropionic acid, the target product, compound g, was obtained. The chemical structure and NMR data of compound ag are shown in Table 1:

[0049] Table 1 Chemical structure and NMR data of compound ag

[0050]

[0051]

[0052] Next, compound ag was subjected to a bacterial quorum sensing inhibitory activity test to evaluate its ability to reduce bioluminescence, i.e., inhibit quorum sensing activity, in the presence of the natural autoinducer 3-oxo-hexanoyl-l-homoserine lactone (OHHL).

[0053] 1. Cell culture

[0054] The test used recombinant Escherichia coli strain NM522, which harbors the sensor plasmid pSB401 and a specific gene from Vibrio fischeri, allowing for quorum sensing activity to be measured through bioluminescence. The natural autoinducer of recombinant E. coli strain NM522 harboring pSB401 is specifically OHHL, a type of AHL. The strain was cultured at 30°C for 18 hours and diluted 10-fold with culture medium using a 96-well plate.

[0055] 2. Test methods

[0056] (1)IC50 IC value: The compound to be tested was diluted in a gradient manner using DMSO solvent, and then competed with 200nM OHHL. The bioluminescence intensity was measured using a microplate reader, and a curve of its relationship with the compound concentration was plotted to obtain the IC value. 50 Value (half maximal inhibitory concentration). IC 50 Commonly used to evaluate drug antimicrobial activity test results, IC 50 The lower the value, the more significant the inhibitory effect of the drug can be achieved at a lower concentration.

[0057] (2) LogP value: The logP value reflects the distribution of a substance between the oil phase and the water phase. A compound with a larger LogP value is more lipophilic, and vice versa, it is more hydrophilic, i.e., more water-soluble. The more hydrophilic a compound is, the higher its inhibitory activity tends to be.

[0058] 3. Test results

[0059] (1)IC 50 The test results are shown in Table 2. As can be seen from Table 2, except for compound a and compound e, all other compounds showed good quorum sensing inhibitory activity, among which compound d and compound g showed inhibitory activity with drug potential (IC 50 This indicates that this class of compounds has a significant inhibitory effect on the Lux system of Vibrio fischeri and the related toxic gene phenotypes it regulates, and can be used as quorum sensing inhibitors to prevent and treat infections caused by drug-resistant bacteria.

[0060] Table 2 IC of compounds 50 value

[0061] Compound <![CDATA[IC 50 Value]]> Compound a ＞200 Compound b 84 Compound c 60 Compound d 20 Compound e ＞200 Compound f 61 Compound g 22

[0062] (2) The logP value test results are shown in Table 3. As can be seen from Table 3, compound a and compound e have higher logP values and lower inhibitory activity. In the structures of compound a and compound e, the thioamide group is connected to the aromatic group, which makes the compound's configuration lack flexibility and restricts the process of binding to the receptor protein. This may be the reason for their lack of inhibitory activity. At the same time, compound d and compound g have lower logP values and tend to exhibit higher inhibitory activity.

[0063] Table 3 logP values of compounds

[0064]

[0065]

Claims

1. N-thioacyl homoserine lactone compounds, characterized in that: The N-thioacyl homoserine lactone compound is used to inhibit bacterial quorum sensing activity, and its general chemical formula is: In the above formula, Ar is an aromatic group; Alkyl is an alkyl group.

2. The N-thioacyl homoserine lactone compound according to claim 1, characterized in that: The N-thioacyl homoserine lactone compound is selected from any one of the following: Compound a: Compound b: Compound c: Compound d: Compound e: Compound f: Compound g:

3. The N-thioacyl homoserine lactone compound according to claim 1 or 2, characterized in that: The N-thioacyl homoserine lactone compound is used for inhibiting the quorum sensing activity of Vibrio fischeri.

4. A method for preparing N-thioacyl homoserine lactone compounds, characterized in that: The preparation method comprises: Step 1: dissolving L-homoserine lactone salt and carboxylic acid in a container, adding triethylamine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and 1-hydroxybenzotriazole monohydrate to the container to react to obtain an intermediate product; Step 2: reacting the intermediate product with Lawesson's reagent to obtain the target product, namely, N-thioacyl homoserine lactone compound.

5. The method for preparing N-thioacyl homoserine lactone compounds according to claim 4, characterized in that: The carboxylic acid is selected from any one of the following: p-bromophenylacetic acid, p-bromobenzoic acid, hexanoic acid, p-nitrophenylpropionic acid, p-bromophenoxyacetic acid, p-methylbenzoic acid, cinnamic acid, and p-nitrophenylpropionic acid.

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